Musical instrument



Nov. 13, 1951 J. w. MCBRIDE MUSICAL INSTRUMENT Filed Aug. 15, 1949 5 Sheets-Sheet l INVENTOR. JOHA/(U. M fiie/fif QTTaQA/EV 1951 .1. w. M BRIDE 2,574,880

MUSICAL INSTRUMENT Filed Aug. 15, 1949 5 Sheets-Sheet 2 INVENTOR. JOHN!- M BQIDE 1951 J. w. M BRIDE MUSICAL INSTRUME T INVENTOR.

JOHN w. MBE/DE BY Z/M/ ATTOENEV NOV. 13, 195] w, MCBRIDE MUSICAL INSTRUMENT 5 Sheets-Sheet 4 Filed Aug. 15, 1349 E, Q. Q. mm .flr- II? I 111E i[ I! il F ovamv n I w 9. mN. WW 3| mw ww M om y INVENTOR. JOHN MBE/OE QTY GENE? NOV. 13, 1951 J. W. Mc 2,574,880

MUSICAL INSTRUMENT Filed Aug. 15; 1949 5 Sheets-Sheet s INVEN TOR.

' JOHN M MB /DE ByW IQTTOENEV Patented Nov. 13, 1951 MUSICAL IN STRUIWEN T John W. McBride, Burbank, Calii'., assignor to Bantar, Incorporated, Burbank, Calif., a corporation of California Application August 15, 1949, Serial N 0. 110,262

23 Claims.

The present invention relates to musical instruments, and more particularly to musical instruments, such as guitars, banjos, and violins, having one or more tensioned strings adapted to be vibrated.

Devices are known for determining the free vibrating length of the string of a musical instrument, through sliding a fret or its equivalent along the string. An object of this invention is to avoid the necessity for sliding the fret along the string by providing for its rolling movement and bodily shifting along the string.

A further object of the invention is to provide an apparatus for bodily rolling an element along a string to vary the free vibrating length of the latter.

Another object of the invention is to provide an improved apparatus capable of varying the pitch in musical instruments by shifting a plurality of inclined plane devices with respect to each other.

Yet another object of the invention is to provide an improved apparatus for conveying an object between different locations.

A further object of the invention is to provide a device for conveying or displacing a movable fret along a tensioned string, with assurance that the fret will maintain its proper relationship to the string during such movement.

Another object of the invention is to provide a device for translating 3. fret bodily along a tensioned string, in which the fret may be made with a minimum of weight, thereby facilitating movement of the fret by decreasing inertia forces acting upon it.

- Still a further object of the invention is to provide a device for moving a fret bodily along a tensioned string, in which the device provides a solid backing or support for the fret against the string, thereby enhancing the duration of the tone emanating from the string.

Another object'of the invention is to create a color light efiect in a musical instrument that is harmonious with the pitch tones being produced. The color eiiect can also be provided without any musical tone.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of several forms in which it may be embodied. Such forms are shown in the drawings accompanying and forming part of the present specification. These forms will now be described in detail, illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a top plan view of a stringed musical instrument embodying the invention;

Fig. 2 is a side view of the instrument shown inFig. 1;

Fig. 3 is a, partial longitudinal section, on an enlarged scale, taken along the line 33 on Fig. 1;

Fig. 4 is a partial longitudinal section, on an enlarged scale, taken along the line 44 on Fig. 1;

Fig. 5 is a cross-section through one of the roller assembly members taken along the line 5-5 on Fig. 3;

Fig. 6 is an enlarged partial cross-section taken along the line 6-45 on Fig. 3;

Fig.7 is an enlarged partial cross-section taken along the line 'l'! on Fig. 3;

Fig. 8 is a top plan view through a portion of another form of the invention, with a roller assembly in one position;

Fig. 9 is a longitudinal section taken along the line 9-9 on Fig. 8, with the roller assembly in another position;

Fig. 10 is a cross-section taken along the line l0l0 on Fig. 9;

Fig. 11 is an exploded isometric view of the guide, light and roller assembly members disclosed in :Figs. 8, 9 and 10;

Fig. 12 is a longitudinal section through still another embodiment of the invention;

Fig. 13 is a cross-section taken along the line l3-l3 on Fig. 12;

Fig. 14 is an isometric projection of still another form of the invention.

In its general aspects, the invention contemplates the movement of a rollable element along and in contact with a tensioned string, to de-- termine the free vibrating length of the latter and the resultant pitch thereof. The rolling element rolls along and in contact with the string, being bodily translated from one position to another by guiding devices that form inclined surfaces or planes. Usually, such inclined surfaces are arranged helically, and are provided on rotatable members that serve to feed the rolling element lengthwise of the tensioned string and in proper engagement therewith.

In the form of the invention illustrated in Figs. 1 to 7, inclusive, the musical instrument includes a body member I0, made of wood or other suitable material, having a string anchoring end or board I l at one end, and an inclined peg board I2 at the other end. Arranged transversely across the upper surface of the body member is a bridge I3 having spaced notches I4 for the reception of the tensioned strings I5 that are to be placed selectively in vibration. The strings pass through these notches I4 and through other notches I6 at the rear of the bridge, to a position therebelow, where a roller orball I1 is secured to each string, and engages-the lower portions of the bridge I3 on opposite sides of the notches I6, to anchor the ends of the strings l5.

From the anchor end of the instrument, the strings are disposed lengthwise along the upper portion of the body member ll! toward the inclined peg board I2. The strings pass through notches I8 in another bridge IS on the peg board I2, being secured to the usual tuning posts 20 in the peg board, which may be rotated, in a known manner, by the pegs 2|. Tightening of the pegs 2i will serve to, stretch the strings I5 between the bridge members I3, I9 and determine the initial tension of, the strings, which may be tuned to the desired frequencies. H p

The strings I5 may be set in vibration, as by plucking, by the. fingers, the vibrations being transmitted to an electrical pick-up 22 disposed in the anchor end II of the body member, for transmission to the desired point. A cover 23 is disposed above and over the anchor end of the strings, and 'also above the electrical pick-up 22, there being a tone control knob 24 extending through the cover for emphasizing certain frequencies transmitted to the electrical pick-up device. v

.Four sets of strings I5 are disclosed in the drawings. One or more sets can be employed, and each set may include one or more strings. Inasmuch as the mechanism for determining the free vibrating length of the strings in each set is essentially the same, a detailed description of the. operating mechanism for one set of strings will sufficeforall.

The free vibrating length of eachstring I5 is. determined ,by shifting a roller assembly 25 lengthwise along the, string, the roller axis being transverse, and preferably at right angles, to the direction which the stringspextend. Each roller assembly includes an intermediate string roller 26 rotatable on ashaft 21 that is fixed to uid rol e .2 on n o iej n th of.- Each guide roller 28 has a fiangeZS f r precluding substantial endwise movement of the roller assembly along its axis. The string rollerisdis posed under a set of strings I5, and engages all strings in such set, exerting an upward force thereon. The guide rollers Zdengage inclined guiding surfaces 39 that are disposed under the strings. These surfaces are preferably formed in helicalfashion, and serve to feed each roller assembly 25 back and forth along the strings Therhelical guidemechanism 3i, embodying the surfaces 36, is disposed in a recess 32 in the body member Id and extends between the anchor endII and peg board end 52 of thelatter. )A shaft or spindle 33 is fixed to the bodymember, as by being welded, or otherwise secured, to a metallic plate 34 extending transversely across the body member It and secured to the latter. A transverse outer bar35 is rotatably mounted on the spindle 33, as well as a transverse inner bar 36. The ends of the outer bar are secured. to two helical guides 37 wound in the same direction, and having the same pitch. or lead. The guide surfaces 30 of .thesehelicalmembers, which may be made of strong, stiff wire, are substantially degrees out of phase. In a similar manner, the ends or outer portion of the inner bar 36 are secured to inner helical guides 33 that are wound in the opposite direction from the outer guides 31, and have substantially the same pitch or lead. The guiding surfaces 39 on the inner members 38 which contact the guide rollers 28 of 7 each roller assembly are also substantially 180 degrees out of phase.

The outer helical guide members 3'! extend toward'the inclined peg board I2, where they are secured to the outer ends of an outer bar 39 fi'xed t'o'an outer or tubular shaft 4 3. Similarly, the innerg'uide members 38 are secured to the outer ends of an inner bar 4| fixed to an inner shaft 43 extending completely through the outer shaft 40, and also through a plate 43, to a location within the inclined peg board I2. The end of this shaft 42 is attached to the supporting member 43'for the shaft.

The'inner helical-guide members 38 are wound with an opposite hand from the outer guide members 3?. That is; one of the guide. members may be equivalent to a steeply pitched, left-' hand helical thread, whereas the other guide member is equivalent to a steeply pitched, righthand helical thread. These guide. members engage the guide roller portions 28 of the roller as-. sembly and cradle the roller therebetwen'. As an example, the guide roller 28 on one end of the roller shaft 27 will-engage the outer helical guide 37 at one side of a vertical plane'through itsaxis, and also the inner helical guide 38 on another side of such plane, providing a spaced two-point support for the roller 28. In like manner, the guide roller 28 on the other endof the roller sh'aft will engage an outer guide '31 and an inner guide 3Bon opposite sides of a central vertical plane through the roller axis. In effect, the roller is cradled by the guides, being held firmly by the tensioned strings I5v in engagement with the helical guide surfaces 36, whereas the latter reactively hold the string roller portion 26 ,in firm engagement with the strings.

The roller assembly 25 is moved along the strings by rotating the inner and outer guides 38, 3! in opposite directions and by the same angua lar extents. These guides are coaxial of one another, inasmuch as the axis of the fixed spindle 33 is coaxial with the axis of the inner shaft 42. They may be rotated equiangular amounts in 0D- posite directions in variousways. As disclosed in the drawingsa pinion 46 is fixed to the inner shaft 42, which is attached to the inner bar 4|, Whereas another pinion 41 is fixed to the outer shaft 42 secured to the outer bar 33. These pinions 45, are of the same diameter, and are mounted adjacent one another. meshes with a lower rack 48 secured to a key t9 slidably mounted in the body member Ii] trans-. Verselyof the shafts 40, 42 whereas the other pinion 4i meshes with an upper rack 58 suitably secured to the same key 49. It is apparent that movement of the key 49 by the persens finger will move the racks 48, 5!! longitudinally, but since they are engaging the pinion's 4%,- dl on opposite sides of the common axis of the latter, the pinions will be rotated in opposite directions, to correspondingly rotate the inner and outer -he1. ical guides 38, 31 in opposite directions.

Inward movement of the key 49 by the persons fingers is resisted by the helical spring 44,- so that removal of such force causes the energystored inzthespring to rotate the pinion 46 fixed to the' One pinion 4t shaft 42 in a reverse direction, which correspondingly shifts the key 49 in the reverse direction, and also the pinion 4'! attached to the outer shaft 45 in the reverse direction.

It is, accordingly, apparent from the foregoing description that longitudinal movement of a key 49 will rotate the helical guides 31, 38 in opposite directions. As the guides are rotated, they will shift the cradle roller assembly 25 longitudinally of the strings l5. The guide rollers 28 at all times have a four-point contact with the helical guides, which positively convey it along the strings, and also hold it in proper assembled relation with respect to the strings. Inasmuch as the string roller portion 26 of the assembly is rotatable on the shaft 21, movement of the assembly along the strings can occur, with the string roller portion rolling under the strings without any sliding friction, thus insuring a smooth operation to the device, with a minimum of extraneous noise. The guide roller flanges 29 prevent substantial endwise movement of the roller assembly 25 by engaging the outer guides 31.

A plurality of sets of strings I5 and roller assemblies 25, and associated mechanism, is disclosed. Each set has its rack and pinion and return spring arrangement, which is the same as the arrangement shown most clearly in Fig. 3. Of course, the racks 48, 55 on the keys 49 are so located and arranged thereon as to engage with only a single set of pinions 45, 41, each key being effective for accomplishing bodily translation of only a single roller assembly 25 along a set of strings.

Four keys are disclosed in the form of the invention shown in Figs. 1 to 7, inclusive, so as to enable the four fingers of the left hand to selectively manipulate the keys 49. If desired, one or more of the keys may be manipulated by a persons foot. For that reason, a pedal operated device is shown in Figs. 3 and 7, one device for each key to which it is applied, as the outermost two keys. Each pedal operated device includes a pedal 55 pivoted to a suitable support or base 56. The outer end of the pedal is pivotally connected to a link 51, extending upwardly toward the instrument, the other end of the link being pivoted to an operating lever 58 mounted on a pin 59 carried by the instrument body if]. The opposite end of the operating lever supports a roller 60 engaging the end of the key 49.

Depression of the pedal 55 will rock the operating lever 58 in counter-clockwise direction, as seen in Fig.7, to shift the key 59 inwardl and bodily translate the roller assembly 25 along the strings i5. Return movement of the pedal 55 is accomplished by the helical spring 44 disposed around the shaft. The force of such spring may be supplemented by disposing another coil spring 5| between the pedal 55 and the supporting base 56, which will tend to elevate the pedal device and remove the inwardly directed force from the key 49.

By appropriate manipulation of the keys #39, each roller assembly 25 may be bodily translated along the length of the one or more strings [5 in each set, and the string appropriately placed in vibration, as by plucking, to produce the desired fundamental notes. The sounds are picked up by the electromagnetic device 22 for transmission to a speaker (not shown) In the form of invention disclosed in Figs. 8 to 11, inclusive, the helical guiding surfaces 35a are formed on tubular members 62, 63. A cylindrical tube is out along two helical lines to provide guiding surfaces 30a displaced substantially degrees from one another in phase. The inner and outer helically cut tubular guides 63, G2 are made in this manner, the inner guide 63 being disposed within the outer guide 82. The outer guide 62 has an end plate 64 welded, or otherwise suitably secured, to it, which is rotatable upon a fixed spindle 33a at the anchor end of the instrument, the other end of the guide 62 being secured to an end plate or filler member 65 attached to the outer shaft 40a. The inner helical guide 63 has end plates 66, 67 secured to it, one end plate 66 being rotatable on the fixed spindle 33a, and the other end plate 6'! being secured to the shaft 42a extending through the outer shaft 40a, in substantially the same manner as in the other form of the invention.

The hel1cal guiding surfaces 3012 on the inner and outer tubular members 63, 62 are relatively disposed in essentially the same manner as in the other form of the invention. The guide rollers 28 of each roller assembly is nested at all times in a concavity 68 formed between the helical guides 52, 63. As before, the helical surfaces 30a on the inner guide 63 are of the opposite hand from the opposite surfaces 30a on the outer guide 62, the guide rollers being cradled in the concavity which these guide surfaces form, as disclosed in Fig. 9, in which a fourpoint contact is provided between the guide rollers 23 and the helical guiding surfaces on the inner and outer tubular members. The same rack and pinion arrangement as in the other form of the invention may be employed for shifting the roller assembly 25 along the strings. In all respects, the operation of the instrument shown in Figs. 8 and 9 is the same as that illustrated in Figs. 1 to 7, inclusive. The advantage of the arrangement shown in Figs. 8 and 9 is that it is more rigid, and may be made with a greater degree of accuracy and assurance of an extended life.

As disclosed in Figs. 8 to 11, inclusive, the tubular members 52, 53 cooperate with one another to form an enclosure except in certain regions, as the particular point at which the roller assembly 25 is located at the time. This enclosure arrangement is availed of to enable color effects to be provided. To accomplish this objective, a fluorescent light tube H3, or other source of illumination, is disposed within the lower portion of the tubular members 62, 53 and extends lengthwise thereof, the tube being supported in end brackets ll, 12. One of the brackets '12 may be fixedly secured in the fixed spindle 33a, whereas the other bracket ll may have an extension 13, piloted within the rotatable shaft 42a, so as not to rotate with the latter. Disposed above the fluorescent light tube H3 is a transparent or semitransparent strip 74, which may possess different colors along its length, these colors being chosen as to correspond with the position of the roller assembly 25 along the strip, and, consequently, with the frequency of vibration emanating from the strings I5. The fluorescent tube 10 itself could be provided with different colors along its length, rather than the transparent or semitransparent strip 14. Current is fed to the tube 10 through suitable leads l5, it, the leads running through and out of the stationary spindle 33a.

As the instrument is being played, the roller 25 is shifted along the strings [5. At the location of the roller 25, the inner and outer tubes 63,

62 are arranged with respect to each other as to the strings.

gsvcsso provide an opening. H through which light fromthe tube 10. can shine upwardly. At other portions. along the helical tubular guides, the light ispresented from showing upwardly. Accordingly, a color light effect can be caused to shine through the instrument that is harmonious with the'pitch tones being produced. For that matter, the color: efiect can be provided merely by rotating the inner andouter tubular guides 63, 62 in opposite directions, without setting the strings into vibration, thereby merely producing color harmony without any musical tones.

In the form ofinvention disclosed in Figs. 12 and 13, a single helical guide 80 is providedfor shifting the roller assembly a lengthwise along Since only a single helical guide is furnished, it is only necessary to provide a-single' rack and pinion arrangement for rotating the guide. Thus, a rack 85- is secured to a key 82 meshing with a-pinion 83 that is fixed to a shaft 84 attached to the helical guide The other end of the helical member is secured to a-spindle- 85 rotatable in a bracket 86 attached to the frame 8101? the instrument. The opposite surfaces or edges88 on the helical guide 86 are substantially 180 degrees from each other, and are arranged to contact the guide roller portions 28a of the roller assemblyholding the string roller portion 26a in engagement with the tensioned strings [5 there-- above These latter strings also hold the roller assembly- 25adownwardly against the helical guide 80 as well as a toothed pinion 89, formed on each roller guide member 28a, in proper engagementwith: a stationary rack 9 arranged lengthwise of andadjacent the helical-guide. Actually, there is a rack Sid-for each pinion 89, and these racks are disposed on opposite-sides oi the helical guide member 80 and extend substantiallyalong itsentire length.

As the helical guide 80 is rotated about its axis in either direction, through appropriate manipulation of the key 32, rack 8|, and pinion 83, the helical surfaces 88 on the guide shift the-roller 25a along its racks 9t and along the strings 5. The meshing of the guide roller pinions- S9 with the guide racks 90 insures proper traverse of'the roller assembly along the strings l5 and its ap-- propriate alignment with all of the 1 operating parts.

In theform of invention disclosed in Fig. 14, the roller assembly 2519- may be shifted along the strings l5 bybod-ily translating a plurality of oppositelyinclined plane devices. The roller assembly 25bis: essentially the same as was de-- scribed in connection with the other forms of the invention. Its stringed roller portion 26b is in contact with one or more tensioned strings l5, Whereas the letter surfaces of theguide roller portions 2% are in engagement with straight guide bars85, A pair of parallel guide bars sii is arranged on oppositesidesoi the strings i5; and are' inclined in one direction. Another-pair-ot'parallel guidebars t5 isdisposed on opposite sides of the strings within the first-mentioned-guide-bars 96, and areinclined in the opposite direction.

The. guide. rollers at one side of a roller as- V same manner as the helical guide surfaces intheother forms of the invention cradle their guidef rollers.

As disclosed in'Fig. 14, the roller assembly 2511'- may be bodily translated lengthwise of the strings l5by moving the guidebars 95, 96 vertically, the

outer inclined guide bars 96 being shifted in'the opposite direction from the inner guide bars To accomplish such movement, the ends of the outer guide bars 96, at one endofthe instrument,

are secured to" the upper portions of outer vertical rackmembers 91, which are attached together as by'useoi a cross-piece 98', the other ends ofthe;

same guide bars 96 are secured to the lower ends of corresponding rack members 9111. The rack members 91, 9.1a occupysubstantially the same elevation, inclining the guide bars it becausethe attachment of the latter to the upper and lower so as to permit-extension offshafts'ltfl' from the" sets of racksSla, 99a at the other end of the in- 'strument.

The outer guide bars 96' are secured'to in ternally toothed racks 9-7, 97a; whereas the inner' guidebars 95am attached to externally'toothed" racks 99, 99a. This toothed arrangement is'pro vided so as to enable the racks to engage pinions 161 that are mounted on a pair of shafts lilil' extending along the instrument. Thus, a pair'of' pinions liil, [0-2 is providedat each endof the instrument, a pinion Hll or I532 at one endbeing secured to the same shaft lilt asthe pinion'l-M or" I02 at the other end, so as to move jointly.

One of the inner racks 99 may be provided with a suitable key "33 for manipulation by the per-=- Depression of the rack 99 willshift sons finger. theinner'inclined guide bars 95 downwardly, and

because oi meshing of these racks with the pinions lfll, I02, will cause the outer guide bars"- 96 to beelevated, or moved in the opposite" direction. The opposite inclination of these bars 96,

95 will cause them to shift-the roller assembly 2571 lengthwise of the string, and thereby determine the free vibrating length thereof. Of course,

movementof the racks 9-9 in the opposite direction will correspondingly shiftthe roller assembly'in' the opposite direction.

It is, accordingly; apparent that the free vibrating' length of the stri-ng of musical instruments can be determined by rollinga member, such as a movable fret, bodily along a tensioned string. Such movement is positive in character, since the upper portion of the movable fret is inengagement with the string or strings I5, and the lower portion with the inclined guiding members. Since the fret is held positively between the strings and the gu-idingmembers, itmay be madeto possess a minimum of weight, since its weight is not afactor in moving it bodily along the-tensioned string. For thatreason, movement of the fret is facilitated because of its light Weightand the accompanying decrease in the inertia forces? acting upon it.

The movable fret or rolling element will always maintain its proper relationship-to the string dur 75 ingitsmovement, because it is positively shifted The opposite inclined However; the guide bars in both directions by the inclined surfaces on the guides. Moreover, these guides provide a solid backing for the fret against the string, serving the purpose of enhancing the duration of the tone emanating from the string. This is especially true of the tubular guide arrangement illustrated in Figs. 8 and 9, which is extremely rigid.

Where color harmony is desired, the shiftable opening of the tubular guide members, accompanied by the variations in the color of the tube along the string, provides very pleasing color effects.

The inventor claims:

,, 1. In a musical instrument: a tensioned string;

a rollable member having a surface in contact with said string; and means providing one or more inclined guiding surfaces in engagement with said surface of said rollable member for bodily translating said rollable member along said. string.

2. In a musical instrument: a tensioned string; a fret member in contact with said string; a rotatable member disposed lengthwise of said string; said rotatable member having an inclined guiding surface thereon engaging said fret member to bodily translate said fret member along the string upon rotation of said rotatable member.

- 3. In a musical instrument: a tensioned string;

a roller member in contact with said string; a rotatable member disposed lengthwise of said string; said rotatable member having a helical guiding surface thereon engaging said roller member to bodily translate said roller member along the string upon rotation of said rotatable member.

4. In a musical instrument: a tensioned'string; a roller member in, contact with said string; a rotatable member disposed lengthwise of said string; said rotatable member having a helical guiding surface thereon engaging said roller member to bodily translate said roller member along the string upon rotation of said rotatable member; said roller member comprising a string engaging portion and a portion engaging said guiding surface and rotatable with respect to said string engaging portion.

5. In a musical instrument: a tensioned string; a fret member in contact with said string; means providing a plurality of guiding surfaces inclined in opposite directions and simultaneously engaging said fret member; and means for moving said guiding surfaces simultaneously in opposite directions to translate said fret member bodily along said string.

6. In a musical instrument: a tensioned string; a roller member in contact with said string; a first rotatable member disposed lengthwise of said string; a second rotatable member disposed lengthwise of said string and located within said first member; said rotatable members having helical guiding surfaces thereon engaging said roller member, the helical surface of said first member being of the opposite hand from the helical surface of said second member; and means for rotating said rotatable members simultaneously in opposite directions to translate said roller member bodily along said string.

7. In a musical instrument; a tensioned string; a roller member in contact with said string; a first rotatable member disposed lengthwise of said string; a second rotatable member disposed lengthwise of said string and located within said first member; said rotatable members having helical guiding surfaces thereon engaging said roller member, the helical surface of said first member being of the opposite hand from the heli cal surface of said second member; and means for rotating said rotatable members simultaneously in opposite directions to translate said roller member bodily along said string; said roller member comprising a central string engaging portion and portions on opposite sides of said central portion engaging said guiding surfaces and rotatable with respect to said central portion.

8. In a musical instrument: a tensioned string; a roller member in contact with said string; a first rotatable member disposed lengthwise of said string and having a pair of helical guiding surfaces displaced substantially degrees from each other and engageable with said roller member; a second rotatable member disposed lengthwise of said string and located within said first rotatable member, said second rotatable member,

having a pair of helical guiding surfaces displaced substantially 180 degrees from each other and engageable with said roller member; the helical surfaces of said first member being of the opposite hand from the helical surfaces of said second member; and means for rotating said rotatable members simultaneously in opposite directions to translate said roller member bodily along said string.

9. In apparatus of the character described; a movable member; a first rotatable member; a second rotatable member located within said first member; said rotatable members having helical guiding surfaces thereon engaging said movable member, the helical surface of said first member being of the opposite hand from the helical surface of said second member; and means for rotating said rotatable members simultaneously in opposite directions to translate said movable member bodily along said rotatable members.

10. In apparatus of the character described: a first rotatable member; a second rotatable member located within said first member; said rotatable members having helical surfaces thereon, the helical surface of said first member being of the opposite hand from the helical surface of said second member; and means for rotating said rotatable members simultaneously in opposite directions.

11. In apparatus of the character described: a first rotatable member; a second rotatable member located within said first member; said rotatable members having helically arranged side surfaces thereon, the helical surface of said first member being of the opposite hand from the helical surface of said second member; means for rotating said rotatable members simultaneously in opposite directions; a source of illumination within said rotatable members for translating light through one or more open portions defined by the helical surfaces of said members.

12. In a musical instrument: a tensioned string; a roller member in contact with said string; a first rotatable member disposed lengthwise of said string; a second rotatable member disposed lengthwise of said string and located within said first member; said rotatable members havin helical guiding surfaces thereon engaging said roller member, the helical surface of said first member being of the opposite hand from the helical surface of said second member; and means for rotating said rotatable members simultaneously in opposite directions to translate said roller member bodily along said string;-

a source of illumination Within said rotatable members for transmitting light through an open portion :defined 'lby'fthe helical guiding surfaces ofisaid rotatable aine'mbers, such open portion ;being. located at the position occupied by said roller member along the string.

.1-3..In a :musical instrument: .a tensioned string; ;a :roller member rin contact withthe string;- a rotatable member disposed lengthwise of :the string and having :a helical surface engaging "said roller member; and a, rack in engagement :with said roller-member.

1'4. In a musical instrument: -a tensioned string; a roller member in. contact with the string; :a rotatable member disposed lengthwise -Of'the string :and having a helical surface engaging said roller member; and stationary racks .on opposite sides {of said rotatablememberiand in engagement withsaid roller member.

15. In .a musical instrument: a tensioned string; a roller member in contact with said string; a first rotatable member disposed lengthwise of said string; a second rotatable member disposed lengthwise of said string; sa-id'rotatable members havinghelical guiding surfaces "thereon engaging said roller member, the helical surface of said first member being of the opposite hand from the helical surface of said second member; and means for rotating said rotatable members simultaneously in opposite directions to translate saidroller member bodily along said string.

. 16. In a -musical instrument: a tensioned string; a fret member disposed below and in contact with said string; means below said f-ret member providing a plurality 'of guiding surfaces inclined in opposite directions and simultaneously engaging said fret member to force said fret memberagainst said string; and means for moving said guiding surfaces simultaneously in opposite directions to translate said fret member bodily along said string.

1'7. In a musical instrument: a tensioned string; a roller member disposed below and in contact with said string; a first rotatable member disposed lengthwise of said str-ingand below said roller member; a second rotatable member disposed lengthwise of said string and located within said first member; said rotatable members having helical guiding surfaces thereon engaging said roller member to urge said roller member upwardly against said tensioned string, the helical surface of said first memberbeing of the opposite-hand from the helical surface .of said second member; and means for rotating said rotatable members slmultaneously in. opposite directions to translate said roller member bodily along said string.

18. In apparatus of the character described;

a movable member; a first rotatable memberaa second rotatable member located within said first member; said rotatable members each having a pair of helical guiding surfaces thereon displaced substantially 180 degrees from each other, and engageable with said movable member, saidhelical surfaces of said first rotatable member being of the opposite handfrom the helical surfaces of said second member; and means ferrotating said rotatable members simultaneously in opposite directions to translate said movable member bodily along said rotatablemembers.

19. In apparatus of the character described: a movable member; a first rotatable member of fragmentary tubular form; a second rotatable member of fragmentary tubular form, said second rotatable member being disposed within said first rotatable member; said rotatable members 12 each having a pair of helical guiding'surfaces thereon extending longitudinally thereof and engageable with said movable member; and means for rotating said rotatable members :si multaneously in opposite directions to trans- 'late said movablemember bodily along said r0 rotating said rotatable members simultaneouslyin opposite directions to translate said movable member bodily along said rotatable'menibers {and a source of illumination within said rotatable members for transmitting light throughan'dpen portion defined by the helical guiding surfaces of said fragmentary tubular rotatable members, such open portion being located at thepositionat which said movable member is in engagement with said rotatable members.

21. In apparatus of the character described: a re lable member; a first rotatable member; a second rotatable member. located within said first member; said rotatable members having helical guiding surfaces thereon engaging said rollable member onone side of a plane through the axis of said rollable member, saidplane bein parallel to the axis of said rotatable members; the helical surface of said first member being :of the opposite hand from the helical surface of said second member; and'means for .rotatingsaid rotatable members simultaneously in opposite directions to translate said rollable member *bodily along said rotatable members.

22. In a device .of the character described: a first-member providingapair of spaced sub-,

stantially parallel guiding :surfaces; a second member providing a pair of'spacled parallel guiding surfaces, the plane :of said guiding surfaces of said. second member intersecting the :plane of said guiding surfaces of said firstmember; movable element extending transversely of said members above the line-of intersection ofthe planes or said guiding surfaces, said movable element contacting the guiding surfaces of said first member on oneside of said lineof 'inter-'= section, and contacting the guiding surfaces of said second member on the other side of said line of intersection; and means for relatively moving said members to translate the'line ofintersection of said planes of said guiding surfaces 'totranslate said movable element supported thereabove.

23. In a device of the character described? a first memberproviding a pair of spaced substantially parallel guiding surfaces; -.a second member providing a .pair of spaced parallel guiding surfaces, the plane ofssaid guiding "surfaces of said second member intersecting the planeof of said members and supported by said surfaces of said members above the line of intersection of the planes of said guiding surfaces, said movable element contacting the guiding surfaces of said first member on one side of said line of in' tersecticn, and contacting the guidingsurface's' of said second member on the other side of said line of intersection; and means for relatively moving said members to translate the'line of in tersection of said planes of said guiding surfaces in a direction inclined with respect to said planes and at substantially half the said angle of intersection thereof to translate said movable element supported thereabove.

JOHN W. McBRIDE.

REFERENCES CITED The following references are of record in the file of this patent:

Number 14 UNITED STATES PATENTS 

